What Is ISP Pinout

ISP (In-System Programming) pinout is a hardware-level access method that allows technicians to communicate directly with the NAND flash storage on a device motherboard — bypassing the main CPU boot sequence entirely. On the Samsung SM-A356B, the UFS flash memory chip is connected to a set of dedicated test pads on the PCB. By identifying and connecting to these pads, a compatible tool can read, write, or erase the UFS partitions directly. This technique is essential when conventional software-based methods, such as USB flashing or EDL mode, are unavailable or non-functional. ISP access on the A356B targets the UFS interface signals: CLK, CMD, DAT0, VCC, VCCQ, and GND, which together form the communication bus between the tool and the storage chip.

When to Use ISP

ISP is the repair method of choice in several critical scenarios:

  • Dead Boot: The device powers on but fails to reach the bootloader or OS, and no USB enumeration occurs.
  • Damaged or Non-Functional USB Port: Physical damage to the USB-C connector makes software flashing impossible, but ISP pads on the board remain accessible.
  • Failed EDL / Download Mode: The device does not enter Emergency Download Mode (EDL) or Samsung Download Mode despite button combinations or test-point shorting.
  • FRP Lock After Hard Reset: Factory Reset Protection cannot be bypassed through the UI or ADB, requiring direct partition erase via ISP.
  • Corrupted Bootloader or Firmware: A failed OTA update or interrupted flash has left the device unresponsive to all standard recovery methods.

SM-A356B ISP Test Points

The ISP test pads on the SM-A356B are located on the rear side of the motherboard, in the vicinity of the UFS flash memory chip. The standard UFS ISP signals required are listed below. Due to the compact PCB layout of the A35, pads are fine-pitch and require magnification to locate accurately.

  • CLK — UFS clock signal pad
  • CMD — Command/data line pad
  • DAT0 — Data line 0 pad
  • VCC — Main storage power supply (2.9V–3.0V)
  • VCCQ — I/O power supply (1.8V)
  • GND — Ground reference pad

Note: Exact pad coordinates and silkscreen labels for the SM-A356B have not been independently verified in our reference database. Technicians should cross-reference a high-resolution board schematic or a trusted ISP pad diagram before proceeding.

How to Access the Pads

Follow these steps to establish an ISP connection on the SM-A356B motherboard:

  • Power off the device completely and disconnect the battery before disassembly.
  • Remove the back cover using a heat gun (around 80°C) and plastic pry tools, then detach the battery connector.
  • Unscrew and remove the motherboard carefully, disconnecting all flex cables.
  • Identify the UFS chip on the rear of the PCB using a microscope or loupe.
  • Clean the target pads with isopropyl alcohol (99%) and a soft brush.
  • Solder fine ISP wires or use a dedicated ISP socket/jig to connect to CLK, CMD, DAT0, VCC, VCCQ, and GND pads.
  • Connect the wires to your ISP tool interface and launch the appropriate software module for the SM-A356B.

Safety Tips and Precautions

Working at the board level on the SM-A356B carries significant risk if proper precautions are not followed:

  • Voltage Limits: VCC must not exceed 3.0V and VCCQ must not exceed 1.8V. Overvoltage will permanently damage the UFS chip.
  • ESD Protection: Always work on an anti-static mat and wear a grounded wrist strap. The Exynos 1380 and UFS chip are highly sensitive to electrostatic discharge.
  • No Battery Power During Connection: Never connect ISP wires with the battery attached. Use only the tool's regulated power supply.
  • Avoid Cold Joints: Poor solder connections on fine pads can cause read errors or brick the device. Use flux and a fine-tip iron.
  • Verify Tool Compatibility: Confirm your ISP tool supports the SM-A356B profile before initiating any read or write operation.

Pin / Test Point Reference

PinDescription
CLKUFS clock signal test pad — Exact pad location unverified — cross-reference board schematic
CMDUFS command/data line test pad — Exact pad location unverified
DAT0UFS data line 0 test pad — Exact pad location unverified
VCCUFS main power supply pad — 2.9V to 3.0V — Do not exceed 3.0V
VCCQUFS I/O power supply pad — 1.8V — Do not exceed 1.8V
GNDGround reference pad — Multiple ground points available on board edge

Tools required: EasyJTAG Plus, UMT (Ultimate Multi Tool), Medusa Pro 2, RIFF Box 2, ISP soldering jig or fine ISP wire set, Microscope or digital loupe, Anti-static mat and wrist strap, Fine-tip soldering iron, Isopropyl alcohol 99%, Heat gun

Supported operations: Read Full Firmware / User Data Backup, Write Firmware (Dead Boot Repair), FRP Erase, IMEI Repair (where legally permitted), Bootloader Partition Restore, EFS Backup and Restore

⚠ Safety note: Do not exceed VCC 3.0V or VCCQ 1.8V. Always disconnect battery before connecting ISP wires. Use ESD protection at all times. Incorrect pad connection may permanently damage the UFS chip or CPU.